In recent years, wind turbines have become larger and larger, leading to rotor diameters which became larger and larger, too. Consequently, rotor blades of wind turbines have become larger and larger as well. A rotor blade of a wind turbine may nowadays easily exceed 50 meters. This leads to a challenge in the structural design of the rotor blades. Furthermore, this leads to a challenge of transportation of the rotor blades from the manufacturing site to the installation site of the wind turbine.
One way to cope with this challenge is the provision of a segmented rotor blade. A segmented rotor blade comprises at least two rotor blade segments. The rotor blade may for example be divided into two equally large rotor blade segments. The rotor blade may also be divided into a first rotor blade segment and a second rotor blade segment, wherein the first rotor blade segment is larger than the second rotor blade segment.
Another option is to provide a main part of the rotor blade as one single piece, but to provide a tip section of the rotor blade as a separate piece. This is particularly advantageous if the tip has a specific shape, for example if the tip section is bent away from the main plane of the rotor blade. Then, particularly, transportation of the rotor blade is facilitated by the separated tip section.
In the PCT application WO 2006/056584 A1 a method of assembling a first section of a windmill arm and a second section of a windmill arm is presented. The method comprises the provision of a connecting piece for connecting the two arm sections and the connection is performed by a bolt embedded into the laminated shell of the respective windmill arm section.
In the European Patent Application EP 2,647,494 A1 a wind turbine blade comprising at least two longitudinal modules is disclosed, wherein the longitudinal modules have joining elements which are embedded in a composite material of the longitudinal module.
In other words, in the state of the art two rotor blade segments are connected with each other by some sort of bolt connection which is at least partly embedded in the shell of the rotor blade. A drawback of this solution is that the thickness and the structure of the laminated shell wherein the bolt connection is embedded to have to be adjusted with the thickness, i.e. the diameter, of the bolt. This means that either the shell has to have a sufficiently large thickness, at least where the bolt connection is performed, and/or the diameter of the bolt has to be sufficiently small. According to the position where the connection of the two rotor blade segments is performed this may pose restrictions to the design of the rotor blade.
Thus, there exists an urgent need to provide a segmented rotor blade with a shell wherein the thickness of the shell is relatively thin at the position of the connection of the two rotor blade segments.